IRS1 and type 2 diabetes mellitus: The importance of IRS1 in insulin signaling has been confirmed in studies showing that this gene is associated with peripheral insulin sensitivity as well as in the regulation of insulin secretion [21,22] and a functional IRS1 variant (Gly972Arg, rs1801278) has been related to T2D risk [23], although some studies have failed to replicate this [24,25].